High-end residential dishwashers have dispensing assemblies mounted in the inside surface of the appliance door. The dispensing assembly dispenses both detergent and rinse agent at appropriate times during a wash cycle. The assembly has two separate compartments or reservoirs, one for each ingredient, with actuator mechanisms to release each agent.
Detergent is added to the dispensing assembly with every load of dishes. A spring-loaded door covers the detergent compartment. In an unlatch mode, the door is open. The consumer adds detergent to the compartment prior to the wash cycle. The door is manually closed and is latched automatically by a spring-loaded pawl. A solenoid or wax motor electrically operates the pawl, to unlatch the door at the proper time during the wash cycle. A spring biases the door open to release the detergent for washing.
The rinse agent compartment consists of a reservoir with a filler cap. The consumer removes the filler cap to add rinse agent. Since only a very small amount of rinse agent is used to wash each load of dishes, rinse agent is only added periodically. During a specific wash cycle, rinse agent is emitted from the reservoir through a port that leads to the exterior surface of the dispensing assembly. It is known to open and close the port via a spring-loaded plunger valve. The normal state of the valve is closed. Opening the valve allows rinse agent to flow through the port and into the dishwasher. The valve can be operated by the same solenoid or wax motor that operates the detergent compartment door, or by a different wax motor or solenoid.
The dispensing assembly is controlled by the dishwasher electronic control module or by an electromechanical timer. With the dispenser loaded with detergent and rinse agent and the appliance door secured, the dishwasher cycle of operation begins. As the wash cycle is reached, the solenoid or wax motor is energized, and the spring-loaded pawl moves to its unlatched position. This releases the detergent door, which springs open to introduce the detergent into the dishwasher. As the solenoid or wax motor is de-energized, the spring-loaded pawl returns to its default latched position while the door itself remains open for the duration of the operating cycle.
As the rinse cycle is reached, the solenoid or wax motor is energized a second time, and the spring-loaded plunger valve is opened. Rinse agent is allowed to flow through the port and is introduced into the dishwasher. As the solenoid or wax motor is de-energized, the valve returns to its default closed position and stems the flow of rinse agent.
To avoid operation of the rinse agent plunger valve during the first actuation, dispensers employing a wax motor use an elaborate system of linkages and springs combined with an alternate-action latching feature. Dispensers using solenoids simply allow the rinse agent valve to open during the very brief first actuation. The cycle time to operate a wax motor is much longer, requiring up to about ten seconds, than is that of a solenoid, which is virtually instantaneous. However, even a very brief open and close of the rinse agent valve at the start of the wash cycle can be wasteful over time and many wash cycles.
Although wax motors and solenoids have operated effectively on dishwasher dispensing assemblies, certain disadvantages are associated with the use of each. Solenoids and wax motors are expensive and relatively large. It is desirable to reduce the profile of components housed in the dishwasher panels and door to maximize the open internal volume for holding dishes. The linkage systems from the wax motor or solenoid can be complex. Operating noise levels can be high. Reduced cost, decreased weight, reduced disposal hazards and improved reliability are further goals for all such devices.
What is needed in the art is a compact, low cost and reliable actuator mechanism for detergent and rinse aid dispenser assemblies in automatic dishwashers.